-1 1 setxrange
-0.3 1 setyrange

/A {-0.7 0} def
/B {0.7 0} def
/M {A B milieu} def

/c {A B diamcercle} def
70 c cpoint /C defpoint

%A C B angledroit
[A B C] polygone
[M C] ligne
M A C 0.12 (-) tripointarc
A C M 0.12 (-) tripointarc
C B M 0.1 (-) tripointarc
M C B 0.1 (-) tripointarc
C B M 0.11 (-) tripointarc
M C B 0.11 (-) tripointarc

[A B C M] points
0 180 c Cercle 

(A) A [1.5 dup] dltext
(B) B [1.5 dup] drtext
(C) C [1.5 dup] uctext
(M) M [1.5 dup] dctext

<latex>
$\rm{Abb}.\,7$
</latex>
0.15 -0.25 [2.0 dup] ultexlabel

<latex>
$\theta$
</latex>
0.31 0.44 [1.6 dup] ultexlabel

<latex>
$\theta$
</latex>
0.62 0.031 [1.6 dup] ultexlabel

<latex>
$\phi$
</latex>
-0.6 -0.02 [1.6 dup] urtexlabel

<latex>
$\phi$
</latex>
0.2 0.45 [1.6 dup] ultexlabel